PORTLAND — Attorney General James E. Tierney’s announcement of his congressional candidacy packs the Democratic primary field for southern Maine’s 1st District seat with five candidates.

Tierney joins Portland City Councilor Linda E. Abromson, state Sen. Thomas H. Andrews, former Maine State Housing Authority director Elizabeth H. Mitchell and former Unity College President Ralph Conant among the candidates seeking their party’s nomination.

At his official announcement Saturday, Tierney told supporters that he would focus his campaign on the issues of drugs, the environment and Maine’s economy.

“The economy is everyone’s business. You can’t clean up the environment and fight drugs unless you address the economic considerations,” Tierney told a handful of well-wishers and reporters at his Portland campaign headquarters.

The 1st District seat is being vacated by Democratic Rep. Joseph E. Brennan, who plans to run for governor, a post he held from 1979 through 1986.

Tierney, 42, served eight years in the Maine House — four as Democratic majority leader. In 1981 he began the first of his five terms as attorney general.

He won the Democratic nomination for governor in 1986 but finished second to Republican John R. McKernan in a race that also included two well-financed independents.

Earlier this month, Tierney fulfilled a pledge to move from his home in Lisbon Falls, which is on the edge of the 2nd District, to a home five miles away in Topsham, part of the 1st District.

“I wanted to be in the district I would represent. My family lives there. I grew up in Brunswick and I went to the University of Maine for undergraduate and law school,” he said by telephone Saturday.

Tierney, who said he expects to spend about $200,000 on his primary campaign, said the race should be a challenging one.

“They’re good people and hard workers,” Tierney said of his opponents.

“The primary and the general election will be tough. I just hope we get a big turnout,” he said.